The present invention relates to an energetic plasticizer comprising eutectic mixture of mixed-formals for use in an insensitive high performance explosive and propellant, and a preparation method thereof.
Bis (2,2-dinitropropyl) formal (BDNPF) is a potent plasticizer used in an insensitive high performance explosive and propellant. However, it has an inherent disadvantage that it is solid at room temperature such that it can not be independently used. Thus, as a plasticizer, an eutectic mixture of BDNPF with its homologue is used.
U.S. Pat. No. 5,648,556 disclosed a plasticizer comprising an eutectic mixture of BDNPF/A, bis(2,2-dinitropropyl) formal/acetal, in which BDNPA keeps BDNPF from crystallizing out. The plasticizer comprising an eutectic mixture of BDNPF/A has been commercially available and wildly used in an explosive and a propellant. But, it is well known that thermal/chemical stability of an acetal group in the BDNPA is lower than that of the formal group in the BDNPF.
U.S. Pat. No. 4,997,499 disclosed a 2-components mixed-formal, BDNPF and 2,2-dinitropropyl 2,2-dinitrobutyl formal (DNPBF), in which DNPBF was used as an inhibitor of crystallization of BDNPF. The 2-components mixed-formal is obtained by reacting a mixture of 2,2-dinitropropanol and 2,2-dinitrobutanol with formaldehyde, but it is also known that about 10% of bis(2,2-dinitropropyl) diformal is always produced as an unfavorable side product.
The 2-components mixed-formal is believed to be superior to the BDNPF/A in terms of the thermal and chemical properties and cost involved. Nevertheless, it has never been realized in the formulation of an explosive and a propellant. It is expected that this is resulted from the difficulty of process and the side product yielded unfavorably in an amount of about 10%.
Therefore, it is an object of the present invention to provide an improved energetic plasticizer having excellent thermal and chemical properties as well as being economic.
Another object of the present invention is to provide a method for preparing the plasticizer.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided an energetic plasticizer comprising an eutectic mixture of bis(2,2-dinitropropyl) formal, 2,2-dinitropropyl 2,2-dinitrobutyl formal and bis(2,2-dinitrobutyl) formal. The plasticizer of the present invention has the following merits: its production cost is low and its thermal and chemical stability is excellent, while it has an energy potent similar to those of conventional plasticizers.
The present invention relates to an energetic plasticizer comprising an eutetic mixture of bis(2,2-dinitropropyl) formal, 2,2-dinitropropyl 2,2-dinitrobutyl formal and bis(2,2-dinitrobutyl) formal. The preferable molar ratio of the BDNPF/DNPBF/BDNPF contained in the plasticizer is in the range of 20xcx9c68%/28xcx9c50%/4xcx9c30%. The plasticizer of the present invention may further contain bis(2,2-dinitropropyl) diformal by less than 5%, preferably by less than 3%, and most preferably by less than 1%.
It was found that the plasticizer comprising the eutectic mixture of the above formulation has not been crystallized out at the temperature of xe2x88x9210xcx9c20xc2x0 C.
The plasticizer may be obtained by reacting 2,2-dinitropropanol and 2,2-dinitrobutanol with formaldehyde source.
More particularly, the method for preparing the plasticizer of the invention comprises:
a) dissolving 2,2-dinitropropanol and 2,2-dinitrobutanol into an organic solvent to form an organic solution, in which the molar ratio of 2,2-dinitropropanol to 2,2-dinitrobutanol is 3:1-6:1;
b) adding to the organic solution a sulfuric acid solution where formaldehyde source was dissolved, wherein the temperature of reaction medium is maintained below 20xc2x0 C.; and
c) separating and purifying the product from the reaction mixture.
The preferable organic solvent used in the reaction is methylene chloride, but not limited thereto. And, the formaldehyde source includes, for example, paraformaldehyde or s-trioxane.
In the plasticizer comprising 3-components mixed-formal obtained by the above-described method, the composition of the BDNPF, DNPBF and BDNPF can be controlled in the range of 20xcx9c68/28xcx9c50/4xcx9c30% by suitable adjusting molar ratio of the starting materials, 2,2-dinitropropanol and 2,2-dinitrobutanol.
Most of all, the present invention is characterized in that the content of the diformal, the by-product, can be reduced by less than 5%, preferably by less than 3%, and most preferably by less than 1%.
Reaction of 2,2-dinitropropanol and 2,2-dinitrobutanol with formaldehyde is shown in scheme 1: 